What is JDBC

Yeah, that's probably the first question we should look into. JDBC means Java Database Connectivity.

JDBC is part of java and defines the components required to interact with a database via java. You will find the interfaces of it located at javax.sql and is supplements by java.sql. Usually when we interact with our database we will use interfaces contained in those packages. They contain several interfaces which define how to implement a Connection, Statement, PreparedStatement, ResultSet, DataSource and Driver.

Connection

The connection interface defines the methods for a database connection. It allows us to send statements and prepared statements to our database.

Statement and PreparedStatement

The statement and prepared statement interfaces allow us to define our SQL statement and send it to the database. The prepared statement allows us additionally to set variables in our SQL query and escapes our input to avoid SQL injection.

ResultSet

The ResultSet is what we get when we read data from our database. It allows to access the value of different columns and going through the rows we selected. You can imagine it as a table with the rows and columns we selected in our statement. It also contains additional metadata about the operation we performed.

DataSource

The DataSource is from the javax.sql package, which represents the newer java sql implementation. It is the successor of the DriverManager class from java.sql. It is no longer recommended to use the DriverManager since java 8 and the introduction of the DataSource class.

Instead of creating a single Connection like the DriverManager does the DataSource is supposed to provide a connection and ensure its validity. However, what the DataSource really does highly depend on the implementation of it. Some implementations only provide a single connection and manage it. Some others provide a custom connection which is kept open and maintained. Some implementations like HikariCP provide a DataSource which maintains a pool of connections. We will look into different DataSource implementations and ultimately end up with HikariCP, which is the state of the art way for connection management and pooling. Most databases only provide basic DataSource implementations which are good for playing around but not really made for real world use.

Driver

The driver is the heart of every JDBC implementation. It is basically the translator between java and your database. You will most likely never use the Driver directly, but it is good to know it is there and that it is important.

If you want to know more take a look at the wikipedia article.